The medical aid charity Medecins Sans Frontieres has said it has treated around 3,600 patients in Syrian hospitals it works with who had “neurotoxic symptoms”, and they report 355 deaths.

MSF say the patients arrived at the hospitals on August 21st, the day Syrian rebel forces say the regime launched a chemical weapons attack. So far the Assad regime has denied the attacks, and has refused access to the site by UN inspectors.

MSF say they have no way to scientifically prove that the patients symptoms were caused by the use of chemical weapons, however MSF Director of Operations Bart Janssens, said “MSF can neither scientifically confirm the cause of these symptoms nor establish who is responsible for the attack,”

“However, the reported symptoms of the patients, in addition to the epidemiological pattern of the events, characterised by the massive influx of patients in a short period of time, the origin of the patients, and the contamination of medical and first aid workers, strongly indicate mass exposure to a neurotoxic agent.

“This would constitute a violation of international humanitarian law, which absolutely prohibits the use of chemical and biological weapons.”

The attack has led to wide spread international condemnation, and calls for the international community to take action against the Assad government. President Obama has previously said the use of chemical weapons would constitute the crossing of a red line and would change his calculations.

Read More: The BBC